1. Field of the Invention
The present invention relates to a non-magnetic toner for one-component development, and more particularly to an oilless fixable toner and a method of preparing the toner, and an image developer, an image forming apparatus, a process cartridge and an image forming method using the toner.
2. Discussion of the Background
Conventional electrophotographic image forming methods include charging the surface of an image bearer (photoreceptor), irradiating the surface thereof to form an electrostatic latent image thereon, developing the electrostatic latent image with a colored toner to form a toner image thereon, transferring the toner image onto a receiving material such as a transfer paper, and fixing the toner image thereon. Dry developing methods used in electrophotographic image forming methods and electrostatic recording methods include a method of using a two-component developer including a toner and a carrier, and a method of using a one-component developer not including a carrier. The former stably produces good images, but is difficult to produce constant-quality images for long periods because the carrier is easy to deteriorate and a mixing ratio of the toner to the carrier (toner concentration) is easy to vary. In addition, image forming apparatuses using the two-component developer are difficult to maintain and downsize. Therefore, the latter method of using the one-component developer is drawing attention.
The method of using the one-component developer typically feeds a toner, i.e., a developer with at least one toner feeding member to visualize an electrostatic latent image formed on a latent image bearer (photoreceptor) with the toner. The toner fed by and on the toner feeding member has to have as thin a layer thickness as possible. Particularly when a one-component developer (toner) having high electric resistivity, the toner layer has to have significantly a thin thickness because of needing to be charged by an image developer. Namely, when the toner layer has a thick thickness, only the surface thereof is charged and it is difficult to uniformly charge the whole toner layer.
As a means of regulating the thickness of the toner layer (hereinafter referred to as a “layer thickness regulator”) on the toner feeding member, various methods are disclosed. For example, a regulation blade (press member) is used as the layer thickness regulator, which faces the toner feeding member and presses the toner fed thereby to regulate the layer thickness thereof. In addition, a roller instead of the blade may contact the surface of the toner feeding member to regulate the layer thickness of a toner.
Recently, in order to downsize and lower cost of a fixer, an oilless fixer excluding a fixing oil applicator or reducing application quantity is mostly used. Therefore, a toner needs to include a release agent (wax) to have offset resistance. However, when a toner includes a wax too much, a free wax and a wax on the surface of a toner increase, resulting in adherence of the toner to a regulation blade or a photoreceptor in an image developer.
This is caused by a wax or a resin. The wax is mentioned above, and the hardness of resin matters. Namely, a soft resin breaks when passing the regulation blade, resulting in adherence thereto with a free wax. Further, solid images having blank spots or striped caused by the adherence are likely to be produced. Particularly, a color toner needs to include a binder resin having a low softening point to satisfy its light transmission, colorability and glossiness, resulting in occasional insufficient heat resistant storageability or aggregation of the toner when stored at high temperature.
A number of methods such as adjustment of wax quantity and improvement of binder resin have been disclosed to improve light transmission, colorability and glossiness of a toner without negative effects to other qualities.
Japanese published unexamined applications Nos. 2003-255741 and 2006-276825 disclose a hybrid resin including conventional condensation polymerization resins an vinyl resins having good affinity with a wax.
A combination of the hybrid resin and a wax can increase the wax and the dispersibility thereof in the toner improves. However, the toner lowers its viscosity and it is difficult to completely prevent the toner from adhering to the regulation blade.
Japanese published unexamined application No. 2004-85605 discloses a hybrid resin including a wax, which is prepared by mixing a mixture of material monomers of polymerization resins having independent reaction routes and a wax.
This method improves the dispersibility of a wax in a toner, however, the hybrid resin obtained from the material monomers alone does not have toughness and the toner occasionally cracks when stirred in an image developer.
Because of these reasons, a need exists for a toner for one-component development, fixable without oil, imparting good separativeness between a fixing member (a heating member and/or a pressure member) and a subject an image is transferred onto such as a recording paper, not adhering to or filming over a regulation member and a photoreceptor in an image developer, an having good developability and glossiness to produce high quality full-color images.